Abstract: The effect of died-pressed binders, such as polyvinyl alcohol (PVA), butyl sodium rubber (BSR) and paraffin wax (PW), on green strength, green density, dimensional stability, residue, sintered compact density and mechanical properties of Ti(C,N)-based cermet was investigated. It was found that the types of the binder had a significant impact on the characteristics of the green compact.
PVA improved dimensional stability of the green compact due to interaction between binder and particle. The glass transition temperature (Tg) of PVA influenced the forming behavior of Ti(C,N)-based cermet powders during died-pressed processing. Some residual moisture was needed to obtain high green strength. PVA had a gradual burnout with a low char residue in nitrogen. Compared with PVA, the influence of binders BSR and PW was also presented and discussed.

Abstract: Residual stress in green compact is an important factor to influence the quality of the compact and corresponding powder metallurgy product. To understand the residual stress, a finite element model is set up to simulate the single and double action pressing, unloading and ejecting of powder compacting process. Results show that compaction type has significant influence on the rule of residual stress state and the double action pressing is more helpful to reduce the risk of cracking than the single action pressing. Also better lubricant condition is beneficial to improve residual stress in the green compact.

Abstract: Nd-Fe-B magnets are used in wide range of industrial applications. In this research we studied the possibility of producing bulk Nd-Fe-B magnetic compact by using the direct cylinder explosive compaction. After compaction the density of compact was measured by the Archimedes method. Highly dense compact (> 98% relative density) without cracks was obtained by this technique. A concentric hole was observed at center of some compacts. The magnetic properties of the compact are Br=7.95KG, iHc=10.5kOe, (BH)max= 14MOe, and these values are same as those before explosive compaction.

Abstract: Utilization of MSC.Marc FEM software, the typical warm compaction process of molybdeum powder was simulated. Influence of processing parameters of warm compaction on green density of molybdenum powder were studied. Furthermore, the commonly defect existing in green body were analyzed. The results show that compaction pressure is an important factor on green density. At the beginning of warm compaction, average relative density rises linearly along with the increasing pressure. The green density increases with the suppression speed increasing, when velocity value reaches 7mm/s the density will not increase anymore. After the value of friction coefficient is greater than 0.1,green density decreases with the friction coefficient increasing. Influence of temperature on compaction is improvement of the lubrication condition, and reduces the friction coefficient. The appearance of axial tensile stress is the important factor which causes delamination and cracks. Internal friction and lubrication condition of powder mixed system is the important reason results in defect.